LINKED PAPER
Nesting success and productivity of a declining European turtle dove (Streptopelia turtur) population in western France). Eraud, C., Lormée, H. 2023. IBIS. DOI: 10.1111/ibi.13168. VIEW
Around 1 in 8 bird species are currently threatened with extinction, and almost half of all birds have declining populations. A key part of halting or reversing these declines is understanding their causes, in order to implement the most effective conservation measures or mitigation strategies. However, this is rarely simple, with multiple factors interacting in often complex ways.
In a recent study in Ibis, Cyril Eraud and Hervé Lormée studied a population of European Turtle Doves (Streptopelia turtur) to better understand their population dynamics and suggest where conservation management strategies could be most effective.
European Turtle Doves
The European Turtle Dove is a Vulnerable trans-Saharan migratory species that has long been in decline. The species faces multiple threats, including droughts, agricultural intensification, and hunting (BirdLife International, 2019). However, it is not clear whether low productivity (too few young fledging each year) or high adult mortality (adult deaths exceeding the population renewal rate), or both, are behind the continuing population declines. To explore this, Eraud & Lormée studied European Turtle Doves in the Réserve Biologique Intégrale de la Sylve d’Argenson in western France across three seasons (2014, 2015, and 2019) using radio-tagging and nest surveys to provide original data on nesting habitat, nest-site characteristics, nesting success, and productivity. Matrix projection models using this data were implemented to estimate population growth rate.
Figure 1. Location of the nests found (black dots, n = 86) during the three study seasons in western France. Forested areas are in grey. Dotted line shows the boundary of the Réserve biologique intégrale de la Sylve d’Argenson, located within the Chizé state forest (the largest forested patch on the map). Map sources: BD Forêt® version 2.0 (Institut national de l’information géographique et forestière), Réserves biologiques – Métropole (Muséum national d’Histoire naturelle)..
Nest-sites, breeding success, and productivity
Previous studies of European Turtle Doves carried out in patchy farmland landscapes had found nests in shrubs, hedgerows, or small woodland patches (Carbonera et al. 2022). However, nests from the studied population differed from this in habitat, height, and tree species, with most found in stands with a developed shrub layer. The median distance between successive nests suggested that pairs had relatively high breeding site fidelity. The average clutch size (± se) of 1.98 ± 0.02 was similar to that reported in previous studies, and the rate of nests successfully fledging at least one young of 38.6% was similar to previously reported values in Britain (e.g. Browne & Aebischer 2004: 34.4%) but lower than rates reported in Europe (e.g. Dias 2016:56–75%).
The daily survival rate (DSR) was found to be 0.959 ± 0.006, with a derived nest survival rate of 0.294, and the model results suggested that higher breeding success occurred in more mature forest stages. DSR was also found to be lower at the end of the season. With the exception of one existing study, the population’s mean productivity of 2.40 ± 0.48 fledglings per season was higher than had been previously reported. However, to halt the population’s decline, even this high productivity would need to increase by about 0.18 additional young to a rate rarely reported in this species. The results suggest that, rather than relying on trying to improve productivity, slightly increasing adult survival rate, or first-year survival rate, could ensure population renewal. The researchers suggest that further studies could expand on these findings across other ecological contexts and investigate the impact of spatial and temporal variation in productivity on population dynamics in the European Turtle Dove.
References
BirdLife International. (2019). Streptopelia turtur. The IUCN Red List of Threatened Species 2019: e.T22690419A154373407. VIEW
Browne, S.J. & Aebischer, N. (2004). Temporal changes in the breeding ecology of European turtle-doves Streptopelia turtur in Britain, and implications for conservation. Ibis 146: 125–137. VIEW
Carboneras, C., Moreno-Zarate, L. & Arroyo, B. (2022). The European turtle dove in the ecotone between woodland and farmland: Multi-scale habitat associations and implications for the design of management interventions. Journal of Ornithology. 163: 339–355. VIEW
Dias, S. (2016). Critérios para a gestão sustentável das populações de rola-brava [Streptopelia turtur (L.)] em Portugal. Padrões de abundância, reprodução e pressão cinegética. PhD Thesis, Instituto Superior de Agronomia, Universidade de Lisboa, Lisbon.
Image credits
Top right: Turtle Dove | Andy Morffew | CC BY 2.0 Wikimedia Commons
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